Directional antenna



Dec. 24, 1929 c. s. FRANKLIN ,7 0,851

DIRECTIONAL ANTENNA Filed Jpne 2. 1926 g A g B CHARLES SAMUEL FRANKUN Fatented Dec, 24, 1929 UNETED STATEg PATENT QFFEQE CHAR-LES SAMUEL FRANKLIN, OF BUCKHUBST HILL, ENGLAND, ASSIGNGB TO RADIO CORPORATION CF AMERICA, A CORPORATION OF DELAW'ARE DIRECTIONAL ANTENNA Application filed June 2, 1526, Serial No. 113,123, and in Great Britain June 30, 1925.

This invention relates to directional antenna systems for radio transmission and reception, which are constructed in the form of a line of separate aerials fed through a system of feeders, so that the phases of the currents in all the aerials are maintained substantially constant.

According to this invention an antenna system for the transmission or reception of wireless telegraphy and telephony comprises a plurality of aerials, some of which are coupled or connected directly to the transmitter or receiver, while the others are maintained in correct current phase by radiation or re radiation from the first mentioned aerials.

The object of this invention is to obtain greater eficiency in directional propagation and reception of radio oscillations.

Another object is the excitation of aerials adjacent to the power aerials in the proper phase relationship.

A. further object is the excitation of the power aerials in proper phase relation.

Further objects and advantages of my invention will appear as set forth more fully in the accompanying specification and by reference to the drawing, in which one form of the antenna arrangement for carrying out my invention is schematically shown- In an antenna system in which each aerial is spaced half a wave length from its neighher on either side, the oscillation voltage induced in any aerial, by radiation from the two adjacent aerials is in correct phase and assists the current impressed upon the said aerial by the feeder coupled to it. The result is that each aerial tends automatically to maintain the correct current phase of the adjacent aerials. It is, therefore, not essential to feed every aerial. Every second or even every third aerial need only be directly fed by the feeders, since each aerial connected to a feeder can energize, by radiation, an aerial on either side of it at a distance of half a wave length. This simplifies the feeding system.

Referring to the drawing aerials 2 and 4, which are energized, are of the type described in my co-pending application, Serial h ft 2,322, filed July 01st, 1925, and each consists of two sections, S one-half wave-length long, located one above the other, and connected by phase reversing coils A and B. Radiation is null or nearly so from the coils or center half wave length portion of the aerials 2 and i, so that radiation takes place only from the upper and lower sections S of the aerials, as is more fully set forth in my copending application referred to above. This result is obtained by concentrating alternate half wave length portions of the wire in a small space to prevent radiation therefrom. In the form of the invention illustrated, the coils A and B connecting the sections 8 are induct-ances of a value equivalent to half a wave length of the aerial wire so that while radiation from the parts A and B is substantially null, the portions 8 which do radiate, are in phase. The polar curve of the radiation from the antenna will be in a direction at right angles to the aerial and to the plane thereof. The sharpness in elevation of the beam radiated will depend on the number of alternate sections and null points in each vertical aerial.

In this manner, the correct phase of the current in the upper and lower sections S is obtained, and the energy beam radiated is directive in elevation.

Radiation may also be suppressed from alternate half wave length portions by doubling such portions back on themselves instead of forming a coil such as has been illustrated.

Referring again to the drawing, 1, 2, 3, 4 and 5, are aerials spaced approximately wave length apart. The sections S of the aerials 2 and 4 are connected by coils A and B and are energized from the transmitter (not shown) through a symmetrically branched feeding system F and aerial transformers T and T The aerials 1, 3 and 5 are not connected to the transmitter and do not contain phasing coils between the sec tions S but they are energized by radiation from the power antennas 2 and i. The aerials 1, 3 and 5 reradiate or reflect the energy radiated from aerials 2 and 4.

It will readily be seen that if the spacing between aljacent aerials is exactly A, wave length, the separate sections S will be maintained in phase. In practice it is not necessary that this spacing be exactly wave length, as by small adjustment of the tune of the sections S of the aerials 1, 3 and 5, the phase of the currents induced therein can be controlled.

1 have found that in an antenna system, constructed as above described, all the aerials can be maintained in phase, and that the said system functions substantially as if all the 'aerials were fed directly from a transmitter by a more complicated system of branched feeders.

- In general, the smaller the spacing between the aerials and the larger the number employed, the nearer the system approaches to an ideal current sheet, while if the spacing is made of the order of two or more halt wave lengths, instead of a single hall wave length, the directional properties of the system in azimuth are to a large extent lost.

This invention is likewise applicable to the reception of radio telegraphy and telephony. In this case, the currents induced in the aerials 1, 3 and 5, from the incoming signal wave, effect by re-radiation the currents induced in the aerials 2 and 4 to a degree dependent upon the direction of origin.

Having thus described my invention, what I claim is:

'1. In a directive antenna system, the combination of a plurality of aerials coupled to a single work circuit, and a plurality of sectional disconnected aerials operated by said first mentioned aerials byradiation andmaintained in correct current phase by being symmetrically spaced therefrom, at a distance of substantially wave length.

2. In a directive antennasystem, the com bination of a plurality of aerials coupled to a work circuit, a plurality of disconnected aerials operated by said first mentioned aerials and maintained in proper current phase by being spaced therefrom a distance equal to substantially wave length, said latter mentioned aerials each comprising a plurality oi electrically insulated sections placed one above the other.

3. In a directive antenna system, the combination of a plurality of aerials coupled to a work circuit, a plurality of disconnected aerials operated by said first mentioned aerials and maintained in proper current phase by being spaced therefrom a distance equal to substantially wave length, said first mentioned aerials comprising a plurality of sections substantially wave length in length and connected by a relatively concentrated inductance of the value of wave length, and said last mentioned aerials comprising a plurality of electrically insulated sections approximately wave in length.

4-. A d ective antenna system comprising a plurality of sectional reflectors, a plurality of radiators alternated with said reflectors and symmetrically spaced relative thereto, and a single means to energize said radiators in phase.

5. A directive antenna system comprising a plurality of refiectos composed of upper and lower sections insulated from each other, means for maintaining said reflector sections in correct phase relationship comprising a plurality of radiators s n'imetrically alternately spaced with'relation to said reflectors, and a common exciting means for said radiators.

6. A directive antenna system comprising a plurality of spaced radiators, inductances in each radiator adapted to suppress radiation from alternate half wave lengths thereof, a plurality of reflectors composed of upper and lower sections alternately and symmetrically spaced relative to said radiators, and means for maintaining said reflectors and radiators in phase including a common means for exciting all of said radiators.

7. A broadside directive antenna system comprising a plurality of aerials lying in a single plane, some of which are maintained in phase by being coupled to a common work circuit and energized thereby, others of which are maintained in correct phase relationship by radiation from the first mentioned energized aerials.

8. A broadside directional antenna system for the transmission or reception of short Waves comprising a plurality of aerials, lying in a single plane, some of which comprise a plurality of radiating sections coupled by phase reversingnonradiating portions, and are maintained in phase by being symmetrically coupled to a common work circuit, others of which are composed of a plurality of electrically insulated. sections and are maintained in correct phase relationship by means of their symmetrical spacing relative to the first mentioned aerials.

9. A broadside directional antenna system for the transmission or reception of short waves comprising a plurality of upright parallel aerials lying in a single plane, alternate aerials having a plurality of half wave length sections coupled by substantially non radiating portions an electrical hallwave in length, a symmetrically branched transmission line system for coupling said aerials to a common work circuit, the other alternate aerials comprising 'a plurality of electrically insulated half wave length sections, said aerials being spaced a halt wave length apart to operate cophasally.

CHAR-LES SAMUEL FRANKLIN. 

